A pressure assisted toilet system typically includes a pressure tank, such as a flushometer tank, a supply system and a flush cartridge. The supply system typically includes a backflow preventor and a pressure regulator to ensure that the pressure tank is maintained below a desired pressure. The pressure tank is fully sealed and maintains the supply pressure during refilling after each flush. This supply pressure, typically 45-55 pounds per square inch gauge (psig), pressurizes the pressure tank to its prescribed level and provides a motive force for a subsequent flush of a toilet bowl. Prior art pressure assisted toilet systems are found in U.S. Pat. Nos. 4,223,698; 5,361,426, 6,360,378 and RE37,921 the disclosures of which are hereby incorporated by reference in their entireties.
FIG. 1 illustrates a prior art pressure assisted toilet system 20. System 20 is normally encased in an outer china housing 22, a pressure tank 24 (such as disclosed in U.S. Pat. No. 5,802,628) having a discharge outlet 28 and an inlet 30, and a flush valve cartridge 36. Flush valve cartridge 36 includes a flush valve 38 having a seal 40, a top flange 42, and an escape hole 44 formed therein, a flush valve stem 46 interposed through the escape hole 44, a flush valve spring 48, a generally cylindrical jacket 50, a lower inlet 52 positioned between the jacket 50 and the discharge outlet 28, and a actuation portion 54. Seal 40 of flush valve 38 seats against discharge outlet 28 in order to allow pressure tank 24 to fill with water. The flush valve stem 46 includes a flush valve enlargement 60 that selectively seals with a portion of the flush valve 38. The top flange 42 is dimensioned so as to provide a small amount of clearance between an outer edge of the top flange 42 and the generally cylindrical inner surface of the jacket 50. When filled with water, the tank 24 is typically pressurized above atmospheric pressure.
To flush system 20, the actuation portion 54 is depressed toward the flush valve 38 which urges the valve stem 46 downward, which permits water (and/or air) to flow through escape hole 44, thereby reducing the pressure above flush valve 38 within cartridge 36. With this pressure reduced, flush valve 38 is forced upward by the pressure differential created between the tank 24 and the area above the flush valve 38 as water flows between the outer edge of the top flange 42 and the jacket 50. That is, the pressure differential across the top flange 42 will overcome the force of the flush valve spring 48 to lift the flush valve 38. As the flush valve 38 lifts, water is discharged through discharge outlet 28. Generally, the flush valve 38 will lift entirely out of the discharge outlet 28 (above the surface that the seal 40 contacts) during each flush to permit a maximum volumetric flow through the discharge outlet 28. After a majority of the water is discharged from the tank 24, the pressure differential across the top flange 42 is reduced and the flush valve spring 48 urges the flush valve to return to a sealing engagement with the discharge outlet 28.
While the ability of a prior art pressure assisted toilet flush system to extract waste is unmatched, a disadvantage is that the noise generated during flushing has been considered undesirably loud. As a result, this has restricted its use in residential applications where excessive noise is undesirable. This noise is partially due to the rapid change in water flow rate, cavitation, and flow direction. What is needed, therefore, is a pressure assisted toilet system that controls the flow of water in such a way that noise is reduced to more acceptable levels.